1. Field of the Invention
The instant disclosure relates to a loudspeaker; more particularly, to a loudspeaker constructed without permanent magnet.
2. Description of Related Art
With the advance in technology, electronic devices are becoming more miniaturized. Some examples of miniaturized devices are radios, portable cassette players, MP3 players, mobile phones, personal digital assistants (PDAs), and laptop computers.
To not disturb others while using abovementioned devices for listening purposes, earphones are used accordingly. Loudspeakers are used to produce sound and play a critical role for various electronic devices. Conventional loudspeakers include a voice coil that sits in front of a permanent magnet. When the electric signals are fed into the coil, the coil either attracts or repels the permanent magnet. The backward and forward movement of the voice coil pulls and pushes a movable membrane. The vibrating movable membrane thus pumps sounds out into the air.
However, the permanent magnet adds more cost to manufacture the loudspeakers, besides occupies additional space inside thereof. In other words, the sheer size and weight of the permanent magnet pose significant challenges in miniaturizing electron devices using conventional loudspeakers. Moreover, the permanent magnet is restricted to have circular shape, which narrows the use of conventional loudspeakers.